Coating agents for producing rigid coatings resistant to scratching and soiling and rigid moulded bodies resistant to scratching and soiling and method for the production thereof

ABSTRACT

The invention relates to coating agents for producing rigid coatings resistant to scratching and soiling which contain: A) 1-30 mass % polymer produced by free radical polymerisation of a mixture containing A1) 1-10 weight parts of at least one sulphur compound containing at least 3 thiol groups and A2) 90-99 weight parts of alkylmethacrylate; B) 0.2-10% mass of at least one fluoralkyl(meth)acrylate having from 3 to 30 carbon atoms in an alcohol radical which comprises from 6 to 61 fluorine atoms; C) 20-80 mass % multifunctional (methyl)acrylate; D) 0.01-10 mass % of at least one initiator; E) 5-75 mass % of at least one solvent and F) 0-40 mass % ordinary additives. The rigid moulded bodies resistant to scratching and soiling and comprising a plastic substrate and scratching resistant coating are also disclosed.

The present invention relates to coating compositions for producingformable scratchproof coatings with dirt repellency effect, to mouldingscoated with these coating compositions, having a scratchproof, formableand dirt-repellent coating, and to processes for producing the coatedmouldings.

Thermoplastically deformable polymers by their nature do not match thescratch resistance of many metals or mineral glasses. The susceptibilityto scratches is manifested to particular disadvantage in transparentpolymers, since the articles in question very quickly lose theiraesthetic quality.

Scratchproof coatings for polymers are known per se. By way of exampledocument DE 195 07 174 describes UV-curing scratchproof coatings forpolymers, which exhibit a particularly high UV stability. These coatingsalready show a good spectrum of properties. However, polymericmouldings, including those with scratchproof coatings, are usedprimarily in the form of panels in outdoor construction, such as insound-proof walls or as glazing for facades, bus shelters, advertisingspaces, advertising pillars, street furniture, where they are subjectboth to natural soiling and to defilement caused by vandalism, such asgraffiti daubings, for example. Cleaning such surfaces is very costlyand inconvenient, since in many cases the surface is attacked as aresult.

In order to solve these problems it is common to add fluorine-containingacrylates to the coating compositions. Coating compositions of this kindare described, for example, in DE 43 19 199.

A disadvantage of known coating compositions, however, is that thecoatings produced from them form cracks on polymeric articles in thecourse of heat forming, the coating on the formed article taking on amilky cloudiness and losing its aesthetic quality.

Subsequent forming of the panels, provided with a hydrophobic andoleophobic coat, however, is desirable for a variety of reasons. Forinstance, in particular, the transport costs for planar panels are lowerthan those of formed articles, owing to the improved stackability.

A further factor to consider is that the production of coated panels andtheir use, for example as a construction component, is carried out bydifferent companies. Accordingly, coated formable constructioncomponents can be manufactured for much wider consumer circles thanpreformed panels produced specifically for one customer.

Furthermore, many particularly advantageous coating techniques, such asroller techniques, for example, are difficult if not impossible toperform on formed components.

In the light of the prior art discussed and indicated herein it wastherefore an object of the present invention to specify coatingcompositions which can be used to produce formable scratchproof coatingswith a dirt repellency effect.

It was thus also an object of the present invention to provide coatingcompositions for producing scratchproof coatings which exhibitparticularly high adhesion to polymeric substrates. This property oughtnot to be impaired by heat forming.

A further object of the invention was that polymeric articles having ascratchproof coating according to the invention should have a highdurability, in particular a high resistance to UV irradiation orweathering.

A further objective of the present invention was to provide coatingcompositions having an anti-graffiti effect which do not adversely alterthe properties of the substrate.

Accordingly, the spray paints used to produce graffiti should as aresult of an anti-graffiti treatment in the course of the invention nolonger adhere, or should adhere only very weakly, to the polymericarticle, with sprayed substrates being easy to clean, so that, forexample, water, cloths, surfactant, pressure washes and mild solventsare sufficient.

A further object of the invention was to provide scratchproofdirt-repellent mouldings which are particularly easy to produce.Accordingly, for producing the mouldings, it ought to be possible inparticular to use substrates which are obtainable by extrusion,injection moulding and by casting techniques.

Another object of the present invention was to specify scratchproofformable dirt-repellent mouldings which exhibit outstanding mechanicalproperties. This property is particularly important for applicationswhere the polymeric articles are to have a high stability to impact.

Furthermore, the mouldings ought to have particularly good opticalproperties.

Another objective of the present invention was to provide scratchproofformable dirt-repellent mouldings which can be adapted simply andlargely to the requirements.

The achievement of these objects and of others which, although notreferred to explicitly, can nevertheless be derived as self-evident fromthe circumstances discussed herein or result automatically from the saidcircumstances, is provided by the coating compositions described inclaim 1. Judicious modifications of the coating compositions of theinvention are protected in the dependent claims appendant to claim 1.

As far as the mouldings are concerned claims 12-21 offer means ofachieving the objects on which they are based.

By virtue of the fact that a coating composition comprises

-   A) from 1 to 30% by weight of a prepolymer obtainable by    free-radically polymerizing a mixture comprising    -   A1) from 1 to 10 parts by weight of at least one sulphur        compound containing at least 3 thiol groups and    -   A2) from 90 to 99 parts by weight of alkyl (meth)acrylates,-   B) from 0.2 to 10% by weight of at least one fluoroalkyl    (meth)acrylate having 3 to 30 carbon atoms in the alcohol residue    and including 6 to 61 fluorine atoms,-   C) from 20 to 80% by weight of polyfunctional (meth)acrylates,-   D) from 0.01 to 10% by weight of at least one initiator,-   E) from 2 to 75% by weight of at least one diluent and-   F) from 0 to 40% by weight of customary additives    it is possible to provide surprisingly scratch-proof dirt-repellent    mouldings which can be heat formed without any cloudiness occurring.

As a result of the measures according to the invention the followingadvantages in particular, among others, are obtained:

-   -   The scratchproof coatings obtained with the coating compositions        of the invention exhibit particularly high adhesion to the        polymeric substrates, and this property is not impaired even by        weathering.    -   The coated mouldings exhibit high resistance to UV irradiation.    -   The coating compositions of the invention and coated mouldings        obtainable from them can be produced inexpensively.    -   Furthermore, polymeric articles coated in accordance with the        invention show a particularly low surface energy. As a result,        the present mouldings are particularly easy to clean.    -   Scratchproof mouldings of the present invention can be adapted        easily to particular requirements. In particular the size and        shape of the polymeric article can be varied within wide ranges        without thereby adversely affecting its formability. Moreover,        the present invention also provides mouldings having outstanding        optical properties.    -   The scratchproof formable dirt-repellent mouldings of the        present invention have good mechanical properties.        Component A

The coating compositions of the invention for producing formablescratchproof coatings with dirt repellency effect contain 1-30% byweight, preferably 2-25% by weight, based on the weight of the coatingcomposition, of a prepolymer obtainable by free-radically polymerizing amixture comprising

-   A1) 1-10 parts by weight, preferably 2-6 parts by weight of at least    one sulphur compound containing at least three thiol groups and-   A2) 90-99 parts by weight, preferably 94-98 parts by weight of alkyl    (meth)acrylates.

Sulphur compounds having more than two thiol groups in the molecule areknown for example from U.S. Pat. No. 4,521,567. The invention isperformed using sulphur compounds having at least three, preferably fourthiol groups in the molecule. The sulphur regulators contain preferablyat least 3, more preferably at least 6 carbon atoms in the molecule, butnot more than 40. The presence of one or, preferably, moreα-mercaptocarboxylic ester groups in the molecule is advantageous,preferably starting from polyols, such as glycerol or pentaerythritol.Examples of suitable sulphur regulators having more than three thiolgroups include 1,2,6-hexanetriol trithioglycolate, trimethylolethanetrithioglycolate, pentaerythritol tetrakis(2-mercaptoacetate),trimethylolethane tri(3-mercaptopropionate), pentaerythritoltetrakis(3-mercaptopropionate), trimethylolpropane trithioglycolate,trimethylolpropane tri(3-mercaptopropionate),tetrakis(3-mercaptopropionato)pentaerythritol, 1,1,1-propanetriyltris(mercaptoacetate), 1,1,1-propanetriyl tris(3-mercaptopropionate),dipentaerythritol hexa(3-mercaptopropionate). Particularly suitable ispentaerythritol tetrakis(2-mercaptoacetate) (pentaerythritoltetrathioglycolate).

The acrylic (meth)acrylates which can be used in accordance with theinvention to prepare the prepolymer are known per se, the expression(meth)acrylate standing for acrylates, methacrylates and for mixtures ofboth. The alkyl (meth)acrylates have preferably 1-20, in particular 1-8carbon atoms.

Examples of the C₁ to C₈ alkyl esters of acrylic acid and of methacrylicacid are methyl acrylate, ethyl acrylate, propyl acrylate, isopropylacrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate and2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate and butyl meth-acrylate. Preferred monomers are methylmethacrylate and n-butyl acrylate.

The prepolymer is prepared using preferably mixtures of alkyl(meth)acrylates containing at least 10% by weight of methyl(meth)acrylate and/or ethyl acrylate and at least 2% by weight of alkyl(meth)acrylates having 3-8 carbon atoms. Preference is given, forexample, to methyl methacrylate fractions of 50-99% by weight, butylmethacrylate fractions of from 5 to 40% by weight and acrylate fractionsof from 2 to 50% by weight.

In the preparation of the thickening polymers it is possible to vary theproportions of regulator to monomers.

The polymerization of regulators and monomers can be conducted inconventional manner as a bulk, suspension or bead, solution or emulsionpolymerization with the aid of free-radical initiators. A suitableprocess for bead polymerization can be taken or derived from DE 33 29765 C2/U.S. Pat. No. 4,521,567, for example (polymerization step stageA).

Suitable free-radical initiators include for example peroxide compoundsor azo compounds (U.S. Pat. No. 2,471,959). Examples that may bementioned include organic peroxides such as dibenzoyl peroxide, laurylperoxide or per esters such as tert-butyl per-2-ethylhexanoate, and azocompounds such as azobisisobutyronitrile.

The thickener polymers obtained can have molecular weights of about 2000to 50,000, depending on polymerization process and regulator fraction.The molecular weight may be determined in particular by viscosimetry,with the prepolymer A) preferably having a viscosity number to DIN ISO1628-6 in the range from 8 to 15 ml/g, in particular from 9 to 13 ml/gand with particular preference from 10 to 12 ml/g, measured in CHCl₃ at20° C.

Component B

The coating compositions of the present invention include as essentialconstituent 0.2-10% by weight, preferably 0.3-5.0% by weight and verypreferably 0.5-2% by weight, based on the total weight of the coatingcomposition, of fluoroalkyl (meth)acrylates having 3-30, preferably 8 to25 and more preferably 10 to 20 carbon atoms in the alcohol residue andincluding 6-61, preferably 7 to 51 and more preferably 9 to 41 fluorineatoms. In addition to the fluorine atoms the alcohol residue of thefluoroalkyl (meth)acrylate may include further substituents. Theseinclude, in particular, ester groups, amide groups, amine groups, nitrogroups and halogen atoms, and this alcohol residue can be either linearor branched.

In accordance with one particular aspect of the present invention afluoroalkyl (meth)acrylate of the formula I is used

in which the radical R₁ is a hydrogen atom or a methyl group and theradical R₂ is a fluorinated alkyl radical of the formula C_(a)H_(b)F_(c)in which a is an integer in the range from 3 to 30, in particular from 8to 25 and more preferably from 10 to 20, b is an integer in the rangefrom 0 to 4 and c is an integer in the range from 6 to 61, preferablyfrom 9 to 41, where c=2a+1−b.

In accordance with one particularly preferred aspect of the presentinvention a fluoroalkyl (meth)acrylate of the formula II is used

in which the radical R₁ is a hydrogen atom or a methyl radical and n isan integer in the range from 2 to 10, preferably from 3 to 8, morepreferably from 3 to 5.

The fluoroalkyl (meth)acrylates present in the coating compositions ofthe invention in accordance with component B) include2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,3,4,4,4-hexafluorobutylmethacrylate, nonadecafluoroisodecyl methacrylate,2,2,3,3,4,4,4-heptafluorobutyl acrylate,3,3,4,4,5,5,6,6,6-nonafluorohexyl acrylate,3,3,4,4,5,5,6,6,6-nonafluorohexyl methacrylate,2,2,3,3,4,4,5,5,6,6,7,7,7-tridecaflurorheptyl acrylate,3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate,3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl methacrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononyl acrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-eicosafluoroundecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-eicosafluorododecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-hen-eicosafluorododecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-hen-eicosafluorododecylmethacrylate,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,15,15,15-tetracosafluoro-2-hydroxy-4(trifluoromethyl)-pentadecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-pentacosafluorotetradecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14-pentacosafluorotetradecylmethacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-nonacosafluorohexadecylacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-nonacosafluorohexadecylmethacrylate,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,17,17,18,18,19,19,20,20,20-heptatriacontafluoroeicosylacrylate.

The fluoroalkyl (meth)acrylates are known compounds, and can be usedindividually or as a mixture.

Component C

To produce a scratchproof coating, in accordance with the inventioncrosslinking monomers are added to the coating composition. Thesepossess at least two polymerizable units, e.g. vinyl groups, permolecule (cf. Brandrup-Immergut Polymer Handbook). They are used inaccordance with the invention in amounts of 20-80% by weight, preferably50-70% by weight, based on the total weight of the coating composition.

Mention may be made of the diesters and higher esters of acrylic andmethacrylic acid with polyhydric alcohols such as glycol, glycerol,trimethylolethane, trimethylolpropane, pentaerythritol, diglycerol,dimethylolpropane, ditrimethylolethane, dipentaerythritol,trimethylhexane-1,6-diol and cyclohexane-1,4-diol.

Examples of crosslinking monomers of this kind include ethylene glycoldiacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate,propylene glycol dimethacrylate, 1,3-butanediol diacrylate,1,3-butanediol dimethacrylate, neopentylglycol diacrylate,neopentylglycol dimethacrylate, diethylene glycol diacrylate, diethyleneglycol dimethacrylate, 4-thioheptanol 2,6-diacrylate, 4-thioheptanol2,6-dimethacrylate, tetraethylene glycol diacrylate, tetraethyleneglycol dimethacrylate, pentanediol diacrylate, pentanedioldimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate,trimethylolpropane tri-(meth)acrylate, dimethylolpropane tetraacrylate,ditrimethylolpropane tetramethacrylate, dipentaerythritol hexaacrylateand dipentaerythritol hexamethacrylate, pentaerythritol triacrylate andpentaerythritol tetraacrylate.

The polyfunctional acrylates and methacrylates can also be oligomers orpolymers, which may also include further functional groups. Mention maybe made in particular of urethane diacrylates and triacrylates orcorresponding ester acrylates.

Component D

The coating composition of the invention is polymerized or cured usingknown initiators which are added to the coating composition in an amountof 0.01-10% by weight, preferably 1-3% by weight, based on the totalweight of the coating composition.

The preferred initiators include those azoinitiators which are widelyknown in the art, such as AIBN and 1,1-azobiscyclohexanecarbonitrile,and also peroxy compounds, such as methyl ethyl ketone peroxide,acetylacetone peroxide, dilauryl peroxide, tert-butylper-2-ethylhexanoate, ketone peroxide, methyl isobutyl ketone peroxide,cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl peroxybenzoate,tert-butyl peroxyisopropyl carbonate,2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate,dicumyl peroxide, 1,1-bis (tert-butylperoxy) cyclohexane,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumylhydroperoxide, tert-butylhydroperoxide, bis-(4-tert-butylcyclohexyl)peroxydicarbonate, mixtures of two or more of the aforementionedcompounds with one another and also mixtures of the aforementionedcompounds with compounds not specified which are likewise able to formfree radicals.

In accordance with one particular aspect of the present invention curingis carried out using photoinitiators, such as UV initiators, forexample. These are compounds which give off free radicals underirradiation by visible or UV light and so initiate the polymerization ofthe coating composition. Customary UV initiators in accordance with DE-A29 28 512, for example, are benzoin, 2-methylbenzoin, benzoin methyl,ethyl or butyl ether, acetoin, benzil, benzil dimethyl ketal orbenzophenone. UV initiators of this kind are available commercially, forexample, from Ciba AG under the trade names ®Darocur 1116, ®Irgacure184, ®Irgacure 907 and from BASF AG under the brand name ®Lucirin TPO.

Examples of photoinitiators which absorb within the short wave visibleregion of light are ®Lucirin TPO and ®Lucirin TPO-L from BASF,Ludwigshafen.

Component E

As diluents it is possible to use both organic solvents and/ormonofunctional reactive diluents. In general the coating compositionscontain from 2 to 75%, preferably from 6 to 50% by weight, based on thetotal weight of the coating composition, of diluents, which can also beused as a mixture.

With the aid of the diluents it is possible to set a coating compositionviscosity in the range from about 10 to about 250 mPa·s. For coatingcompositions which are intended for flow coating or dip coatingoperations it is more customary to use low viscosities of about 1-20mPa·s. In these coating materials it is possible in particular to useorganic solvents in concentrations of up to 75% by weight. For knifecoating or roller application coating purposes the appropriateviscosities are situated within the range from 20 to 250 mPa·s. Thevalues stated are to be regarded merely as guideline values and refer tothe measurement of the viscosity at 20° C. with a rotational viscometerin accordance with DIN 53 019.

In the case of coating materials for roller application processes it ispreferred to use monofunctional reactive diluents. Customaryconcentrations are between 5 and 25% by weight. Alternatively or incombination, however, it is also possible to use organic solvents asdiluents.

The monofunctional reactive diluents contribute to good levellingproperties of the coating material and hence to good processingproperties. The monofunctional reactive diluents possess afree-radically polymerizable group, generally a vinyl function.

These include, inter alia, 1-alkenes, such as hex-1-ene, hept-1-ene;branched alkenes, such as vinylcyclohexane, 3,3-dimethyl-1-propene,3-methyl-1-diisobutylene, 4-methylpent-1-ene, for example;

-   acrylonitrile; vinyl esters, such as vinyl acetate; styrene,    substituted styrenes having an alkyl substituent in the side chain,    such as α-methylstyrene and α-ethylstyrene, for example, substituted    styrenes having an alkyl substituent on the ring, such as    vinyltoluene and p-methylstyrene, halogenated styrenes, such as    monochlorostyrenes, dichlorostyrenes, tribromostyrenes and    tetrabromostyrenes, for example;-   heterocyclic vinyl compounds, such as 2-vinylpyridine,    3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,    2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine,    9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole,    1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,    2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,    N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran,    vinylthiophene, vinylthiolane, vinylthiazoles and hydrogenated    vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles;-   vinyl and isoprenyl ethers;-   maleic acid derivatives, such as maleic anhydride, methylmaleic    anhydride, maleimide and methylmaleimide, for example;-   and (meth)acrylates, with (meth)acrylates being particularly    preferred. The expression (meth)acrylates embraces methacrylates and    acrylates and also mixtures of both.

These monomers are widely known. They include (meth)acrylates derivedfrom saturated alcohols, such as methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate,tert-butyl (meth)acrylate, pentyl (meth)acrylate and 2-ethylhexyl(meth)acrylate, for example;

-   (meth)acrylates derived from unsaturated alcohols, such as oleyl    (meth)acrylate, 2-propynyl (meth)acrylate, allyl (meth)acrylate,    vinyl (meth)acrylate, for example;-   aryl (meth)acrylates, such as benzyl (meth)acrylate or phenyl    (meth)acrylate, it being possible for each of the aryl radicals to    be unsubstituted or to be substituted up to four times;-   cycloalkyl (meth)acrylates, such as 3-vinylcyclohexyl    (meth)acrylate, bornyl (meth)acrylate;-   hydroxyalkyl (meth)acrylates, such as-   3-hydroxypropyl (meth)acrylate,-   3,4-dihydroxybutyl (meth)acrylate,-   2-hydroxyethyl (meth)acrylate,-   2-hydroxypropyl (meth)acrylate;-   glycol di(meth)acrylates, such as 1,4-butanediol di(meth)acrylate,-   (meth)acrylates of ether alcohols, such as tetrahydrofurfuryl    (meth)acrylate, vinyloxyethoxyethyl (meth)acrylate;-   amides and nitriles of (meth)acrylic acid, such as-   N-(3-dimethylaminopropyl)(meth)acrylamide,-   N-(diethylphosphono)(meth)acrylamide,-   1-methacryloylamido-2-methyl-2-propanol;-   sulphur-containing methacrylates, such as-   ethylsulphinylethyl (meth)acrylate,-   4-thiocyanatobutyl (meth)acrylate,-   ethylsulphonylethyl (meth)acrylate,-   thiocyanatomethyl (meth)acrylate,-   methylsulphinylmethyl (meth)acrylate and-   bis((meth)acryloyloxyethyl) sulphide.

Examples of particularly preferred monofunctional reactive diluents arebutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,hydroxypropyl acrylate, hydroxypropyl methacrylate, 2-ethoxyethylmethacrylate or 2,2,3,3-tetrafluoropropyl methacrylate, methylmethacrylate, tert-butyl methacrylate, isobornyl methacrylate.

EP 0 035 272 describes customary organic solvents for coatingcompositions for scratchproof coating materials, which can be used asdiluents. Suitable, for example, are alcohols such as ethanol,isopropanol, n-propanol, isobutyl alcohol and n-butyl alcohol,methoxypropanol, methoxyethanol. Aromatic solvents as well, such asbenzene, toluene or xylene, for example, can be used. Ketones such asacetone or methyl ethyl ketone, for example, are suitable. It is alsopossible to use ether compounds such as diethyl ether or ester compoundssuch as ethyl acetate, n-butyl acetate or ethyl propionate, for example.The compounds can be used alone or in combination.

Component F

By customary additives are meant additions customary for coatingcompositions for scratchproof coatings, which may be present optionallyin amounts of 0-40% by weight, in particular from 0 to 20% by weight.The use of these additives is regarded as being not critical for theinvention.

Mention may be made here, for example, of surface-active substances, bymeans of which it is possible to regulate the surface tension of thecoating formulation and to achieve good application properties. For thispurpose it is possible to make use in accordance with EP 0 035 272, forexample, of silicones, such as various polymethylsiloxane types, inconcentrations of from 0.0001 to 2% by weight.

Another very common additive are UV absorbers, which may be present inconcentrations of, for example, from 0.2 to 20% by weight, preferablyfrom 2 to 8% by weight. UV absorbers can be selected, for example, fromthe group consisting of hydroxybenzotriazoles, triazines andhydroxybenzophenones (see e.g. EP 247 480).

The coating composition of the invention is intended for producingscratchproof weathering-resistant coatings on polymeric substrates.These include, in particular, polycarbonates, polystyrenes, polyesters,such as polyethylene terephthalate (PET), which may also have beenmodified with glycol, and polybutylene terephthalate (PBT),cycloolefinic copolymers (COCs), acrylic nitrides/butadiene/styrene[sic] copolymers and/or poly(meth)acrylates.

Preference is given here to polycarbonates, cycloolefinic polymers andpoly(meth)acrylates, with poly(meth)acrylates being particularlypreferred.

Polycarbonates are known in the art. Polycarbonates can be consideredformally as being polyesters of carbonic acid and aliphatic or aromaticdihydroxy compounds. They are easily accessible through reaction ofdiglycols or bisphenols with phosgene and/or carbonic diesters inpolycondensation or transesterification reactions.

Preference is given here to polycarbonates derived from bisphenols.These bisphenols include in particular 2,2-bis(4-hydroxyphenyl)propane(bisphenol A), 2,2-bis-(4-hydroxyphenyl)butane (bisphenol B),1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol C),2,2′-methylenediphenol (bisphenol F),2,2-bis(3,5-dibromo-4-hydroxyphenyl)-propane (tetrabromobisphenol A) and2,2-bis(3,5-di-methyl-4-hydroxyphenyl)propane (tetramethylbisphenol A).

Normally aromatic polycarbonates of this kind are prepared byinterfacial polycondensation or transesterification, with details beingpresent in Encycl. Polym. Sci. Engng. 11, 648-718.

In interfacial polycondensation the bisphenols are emulsified as anaqueous alkaline solution in inert organic solvents, such as methylenechloride, chlorobenzene or tetrahydrofuran, for example, and are reactedin a staged reaction with phosgene.

Amines are employed as catalysts, and phase transfer catalysts as wellare employed in the case of sterically hindered bisphenols. Theresulting polymers are soluble in the organic solvents used.

Through the choice of bisphenols it is possible to vary the propertiesof the polymers widely. Where different bisphenols are usedsimultaneously it is also possible to construct block polymers inmultistage polycondensations.

Cycloolefinic polymers are polymers obtainable using cyclic olefins,especially polycyclic olefins.

Cyclic olefins include, for example, monocyclic olefins, such ascyclopentene, cyclopentadiene, cyclohexene, cycloheptene andcyclooctene, and also alkyl derivatives of these monocyclic olefinshaving 1 to 3 carbon atoms, such as methyl, ethyl or propyl, such asmethylcyclohexene or dimethylcyclohexene, for example, and also acrylateand/or methacrylate derivatives of these monocyclic compounds. Inaddition it is also possible to use cycloalkanes having olefinic sidechains as cyclic olefins, such as cyclopentyl meth-acrylate, forexample.

Preference is given to bridged polycyclic olefin compounds. Thesepolycyclic olefin compounds can contain the double bond either in thering, in which case they are bridged polycyclic cycloalkenes, or in sidechains. In this case the compounds in question are vinyl derivatives,allyloxycarboxy derivatives and (meth)acryloyloxy derivatives ofpolycyclic cycloalkane compounds. These compounds may additionally havealkyl, aryl or aralkyl substituents.

Exemplary polycyclic compounds, without any restriction being intended,include bicyclo[2.2.1]hept-2-ene (norbornene),bicyclo[2.2.1]hept-2,5-diene (2,5-norbornadiene),ethylbicyclo[2.2.1]hept-2-ene (ethylnorbornene),ethylidenebicyclo[2.2.1]hept-2-ene (ethylidene-2-norbornene),phenylbicyclo[2.2.1]hept-2-ene, bicyclo[4.3.0]nona-3,8-diene,tricyclo-[4.3.0.1^(2,5)]-3-decene, tricyclo[4.3.0.1^(2,5)]-3,8-decene(3,8-dihydrodicyclopentadiene), tricyclo[4.4.0.1^(2,5)]-3-undecene,tetracyclo[4.4.0.1^(2,5),1^(7,10)]-3-dodecene,ethylidenetetracyclo[4.4.0.1^(2,5),1^(7,10)]-3-dodecene,methyloxycarbonyltetracyclo[4.4.0.1^(2,5),1^(7,10)]-3-dodecene,ethylidene-9-ethyltetracyclo[4.4.0.1^(2,5),1^(7,10)]-3-dodecene,pentacyclo[4.7.0.1^(2,5),O,O^(3,13),1^(9,12)]-3-pentadecene,pentacyclo[6.1.1^(3,6),0^(2,7),0^(9,13)]-4-pentadecene,hexacyclo[6.6.1.1^(3,6),1^(10,13),0^(2,7),0^(9,14)]-4-heptadecene,dimethylhexacyclo[6.6.1.1^(3,6),1^(10,13),0^(2,7),0^(9,14)]-4-heptadecene,bis(allyloxycarboxy)tricyclo[4.3.0.1^(2,5)]decane,bis(methacryloyloxy)tricyclo[4.3.0.1^(2,5)]decane,bis(acryloyloxy)tricyclo[4.3.0.1^(2,5)]decane.

The cycloolefinic polymers are prepared using at least one of theabove-described cycloolefinic compounds, particularly the polycyclichydrocarbon compounds. In the preparation of the cycloolefinic polymersit is additionally possible to use further olefins which can becopolymerized with the aforementioned cycloolefinic monomers. Theseinclude ethylene, propylene, isoprene, butadiene, methylpentene, styreneand vinyltoluene.

The majority of the abovementioned olefins, including in particular thecycloolefins and polycycloolefins, can be obtained commercially.Furthermore, many cyclic and polycyclic olefins are obtainable by meansof Diels-Alder addition reactions.

The cycloolefinic polymers can be prepared conventionally, as set outinter alia in Japanese patents 11818/1972, 43412/1983, 1442/1986 and19761/1987 and in Japanese laid-open specifications No. 75700/1975,129434/1980, 127728/1983, 168708/1985, 271308,1986, 221118/1988 and180976/1990 and in European patent applications EP-A-0 6 610 851, EP-A-06 485 893, EP-A-0 6 407 870 and EP-A-0 6 688 801.

The cycloolefinic polymers can be polymerized, for example, usingaluminium compounds, vanadium compounds, tungsten compounds or boroncompounds as catalyst in a solvent.

It is assumed that the polymerization is able to take place with ringopening or with opening of the double bond depending on the conditions,in particular on the catalyst employed.

A further possibility is to obtain cycloolefinic polymers byfree-radical polymerization, using light or an initiator to form freeradicals. This applies in particular to the acryloyl derivatives of thecycloolefins and/or cycloalkanes. This kind of polymerization can becarried out both in solution and without solvent.

A further preferred polymeric substrate comprises poly(meth)acrylates.These polymers are generally obtained by free-radical polymerization ofmixtures comprising (meth)acrylates. These have been described above;depending on preparation, both monofunctional and polyfunctional(meth)acrylates can be used, which are described under component C) andE).

In accordance with one preferred aspect of the present invention thesemixtures contain at least 40% by weight, preferably at least 60% byweight and more preferably at least 80% by weight, based on the weightof the monomers, of methyl methacrylate.

Besides the (meth)acrylates described above the compositions to bepolymerized may also include further unsaturated monomers which arecopolymerizable with methyl methacrylate and with the aforementioned(meth)acrylates. Examples thereof have been set out in more detail inparticular under component E).

Generally speaking these comonomers are used in an amount of from 0 to60% by weight, preferably from 0 to 40% by weight and more preferablyfrom 0 to 20% by weight, based on the weight of the monomers, it beingpossible to use the compounds individually or as a mixture.

The polymerization is generally initiated with known free-radicalinitiators, described in particular under component D). These compoundsare frequently used in an amount of from 0.01 to 3% by weight,preferably from 0.05 to 1% by weight, based on the weight of themonomers.

The aforementioned polymers may be used individually or as a mixture. Inthis case it is also possible to use different polycarbonates,poly(meth)acrylates or cycloolefinic polymers, which differ, forexample, in molecular weight or in monomer composition.

The polymeric substrates of the invention can be produced, for example,from moulding compounds of the aforementioned polymers. In this contextit is generally the case that thermoplastic shaping processes areemployed, such as extrusion or injection moulding.

The weight-average molecular weight, M_(w), of the homopolymers and/orcopolymers for use in accordance with the invention as a mouldingcompound for producing the polymeric substrates, can vary within wideranges, the molecular weight normally being harmonized with the intendedapplication and with the processing mode of the moulding compound.

In general, however, it is within the range between 20,000 and 1,000,000g/mol, preferably from 50,000 to 500,000 g/mol and more preferably from80,000 to 300,000 g/mol, without thereby making any restriction. Thisparameter can be determined, for example, by means of gel permeationchromatography.

The polymeric substrates may additionally be produced by cell castingprocesses. In this case, for example, suitable (meth)acrylic blends arecharged to a mould and polymerized. Such (meth)acrylic blends generallycomprise the above-described (meth)acrylates, especially methylmethacrylate. The (meth)acrylic blends may further comprise theabove-described copolymers and also—especially for adjusting theviscosity—polymers, especially poly(meth)acrylates.

The weight-average molecular weight M_(w) of the polymers produced bycell casting processes is generally higher than the molecular weight ofpolymers which are used in moulding compounds. This results in a numberof known advantages. The weight-average molecular weight of polymersproduced by cell casting processes is generally in the range from500,000 to 10,000,000 g/mol, with no resultant intended restriction.

Preferred polymeric substrates produced by the cell casting process canbe obtained from Degussa, BU PLEXIGLAS, Darmstadt under the trade namePLEXIGLAS®GS or from Cyro Inc. USA, commercially, under the trade name®Acrylite.

In addition, the moulding compounds to be used to produce the polymericsubstrates, and also the acrylic resins, may comprise additives of allkinds. These include antistats, antioxidants, mould release agents,flame retardants, lubricants, dyes, flow improvers, fillers, lightstabilizers and organophosphorous compounds, such as phosphoric esters,phosphoric diesters and phosphoric monoesters, phosphites,phosphorinanes, phospholanes or phosphonates, pigments, weatheringstabilizers and plasticizers. The amount of additives, however, isrestricted in relation to end application.

Particularly preferred moulding compounds comprising poly(meth)acrylatesare available commercially under the trade name PLEXIGLAS® from Degussa,BU PLEXIGLAS, Darmstadt or under the trade name ®Acrylite from Cyro Inc.USA. Preferred moulding compounds comprising cycloolefinic polymers maybe obtained under the trade name ®Topas from Ticona and ®Zeonex fromNippon Zeon. Polycarbonate moulding compounds are available, forexample, under the trade name ®Makrolon from Bayer or ®Lexan fromGeneral Electric.

With particular preference the polymeric substrate contains at least 80%by weight, in particular at least 90% by weight, based on the totalweight of the substrate, of poly(meth)acrylates, polycarbonates and/orcycloolefinic polymers. With particular preference the polymericsubstrates are composed of polymethyl methacrylate, it being possiblefor the polymethyl methacrylate to include customary additives.

In accordance with one preferred embodiment it is possible for polymericsubstrates to have an impact strength to ISO 179/1 of at least 10 mJ/m²,preferably at least 15 kJ/m².

Neither the shape nor the size of the polymeric substrate is critical tothe present invention. In general the substrates used are often in theform of panels or sheets, with a thickness in the range from 1 mm to 200mm, in particular from 5 to 30 mm.

The mouldings can be vacuum-formed components, blow-moulded components,injection-moulded components or extruded polymeric components, which areused, for example, as construction elements outdoors, as components ofautomobiles, casing components, constituents of kitchens or sanitaryinstallations.

The coating compositions are particularly suitable for solid planarsheets and sandwich sheets or multi-wall sheets. Customary dimensions,for example, for solid sheets are in the range from 3×500 to 2000×2000to 6000 mm (thickness×width×length). Sandwich sheets can have athickness of from about 16 to 32 mm.

Before the polymeric substrates are given a coating they can beactivated by appropriate methods in order to enhance the adhesion. Forthis purpose it is possible, for example, to treat the polymericsubstrate by a chemical and/or physical process, the particular processbeing dependent on the polymeric substrate.

The coating blends described above can be applied to the polymericsubstrates by any known method. Such methods include dipping, spraying,knife coating, flow coating and roller coating methods.

The coating composition is preferably applied to polymeric articles suchthat the thickness of the cured coat is from 1 to 50 μm, preferably from5 to 30 μm. At coat thicknesses below 1 μm the weathering protection andscratch resistance is in many cases inadequate; at coat thicknesses ofmore than 50 μm it is possible for cracking to occur under flexuralstress.

After the coating film has been applied to the polymeric article,polymerization takes place, and can be performed thermally or by meansof UV radiation. Polymerization can advantageously be carried out underan inert atmosphere in order to exclude the polymerization-inhibitingatmospheric oxygen, e.g. under nitrogen blanketing. This, however, isnot an indispensable prerequisite.

The polymerization is normally performed at temperatures below the glasstransition temperature of the polymeric article. The applied coatingcomposition is preferably cured by UV irradiation. The UV irradiationtime necessary for this purpose depends on the temperature and on thechemical composition of the coating material, on the nature and power ofthe UV source, on its distance from the coating composition, and onwhether there is an inert atmosphere. The guideline value may be fromseveral seconds to a few minutes. The corresponding UV source shouldemit radiation in the range from about 150 to 400 nm, preferably with amaximum between 250 and 280 nm. The irradiated energy should amount toapproximately 50-4000 mJ/cm². As a guideline value for the distance ofthe UV source from the coating film it is possible to specify from about100 to 200 mm.

The mouldings of the present invention lend themselves outstandingly tothermal forming without damage as a result to their scratchproofdirt-repellent coating. Forming is known to the person skilled in theart. In this operation the moulding is heated and formed by means of anappropriate template. The temperature at which forming takes placedepends on the softening temperature of the substrate from which thepolymeric article has been produced. The other parameters, such as theforming rate and forming force, are likewise dependent on the polymer,and these parameters are known to the person skilled in the art. Amongthe forming methods, particular preference is given to bending methods.Such methods are used in particular for the processing of casttransparent sheets. Further details are found in “Acrylglas undPolycarbonat richtig Be- und Verarbeiten” [Correct machining and use oftransparent acrylic sheet and polycarbonate] by H. Kaufmann et al.,published by Technologie-Transfer-Ring Handwerk NRW, and in VDI [Germanengineers' association] guideline 2008 sheet 1 and also DIN 8580/9/.

The mouldings of the present invention provided with a scratchproofdirt-repellent coating exhibit high scratch resistance. The increase inhaze after a scratch resistance test to DIN 52 347 E (applied force=5.4N, number of cycles=100) is preferably not more than 10%, morepreferably not more than 5% and very preferably not more than 2.5%.

In accordance with one particular aspect of the present invention themoulding is transparent, the transparency TD65/10 to DIN 5033 being atleast 70%, preferably at least 75%.

Without any attendant resultant restriction, the moulding preferably hasan elasticity modulus to ISO 527-2 of at least 1000 MPa, in particularat least 1500 MPa.

The mouldings of the invention are generally very stable to weathering.Thus the weathering stability to DIN 53387 (Xenotest) is at least 4000hours.

Without any attendant resultant restriction, the yellowness index to DIN6167 (D65/10) of preferred mouldings is less than or equal to 8,preferably less than or equal to 5, even after long UV irradiation formore than 5000 hours.

The anti-graffiti effect is obtained by making the surface repellent towater. This is reflected in a large contact angle withalpha-bromonaphthalene, which has a surface tension of 44.4 mN/m. Inaccordance with one particular aspect of the present invention thecontact angle of alpha-bromonaphthalene with the surface of thepolymeric article after the scratchproof coating has cured is preferablyat least 50°, in particular at least 70° and more preferably at least75° at 20° C., without any attendant resultant restriction.

The contact angle with water at 20° C., in accordance with oneparticular embodiment, is preferably at least 80°, in particular atleast 90° and with particular preference at least 100°

The contact angle can be determined using a G40 contact angle measuringsystem from Krüss, Hamburg, the procedure being described in the G40contact angle measurement system user handbook, 1993. The measurement ismade at 20° C.

The mouldings of the present invention can be used, for example, in theconstruction sector, particularly for producing glasshouses orconservatories, or as sound-proofing walls.

The invention is explained in more detail below by means of inventiveand comparative examples, without any intention that the inventionshould be restricted to these examples.

INVENTIVE EXAMPLE 1

A coating composition was prepared containing

-   16.6 parts by weight of pentaerythrityl tetraacrylate,-   66.4 parts by weight of 1,6-hexanediol diacrylate,-   10 parts by weight of 2-hydroxyethyl methacrylate,-   5 parts by weight of PLEX 8770 (prepolymer obtainable from Röhm GmbH    & Co. KG, copolymer of methyl methacrylate, butyl methacrylate and    pentaerythrityl tetrathioglycolate),-   2 parts by weight of Irgacure 184,-   1 part by weight of Zonyl TA-N (fluoroacrylate of the composition:    with R2=CH2CH2(CF2CF2)_(x)CF2CF3 where x=2 to 4, available from    DuPont and    3 parts by weight of Tinuvin 1130, available from Ciba AG.

The coating composition obtained in this way is applied to ®Makrolon(available from Bayer AG) sheets using a spiral-wound wire doctor (12 μmwet film thickness) and after two minutes in each case is cured using ahigh-pressure mercury lamp F 450 from Fusion Systems at a rate ofadvance of 1 m/min under a nitrogen atmosphere.

The coated sheet is formed by the bending method of DIN 8580/9/over atemplate at a temperature of 150° C. The bending radius in theexperiment was 120 mm. The sheet was subjected to a Taber test to DIN52347 to determine the scratch resistance and to a cross-cut to DIN53151. The Taber test was carried out with an applied force of 5.4 Nwith 100 cycles, using a “CS10F” friction wheel from Teledyne Taber.

The results obtained are set down in Table 1. TABLE 1 Taber testCross-cut (DIN 52347) (DIN 53151) Delta-haze Before forming Gt. 0 2.7%After forming (20 minutes at 150° C.) Gt: 0 2.4%

Surprisingly it is found that the scratch resistance is improved by theforming operation. The elongation at break is 5.9%. In order todetermine the dirt repellency effect the coating is sprayed withdifferent paints. After 24 hours the coating of paint is cleaned forabout one minute using a pressure washer at 80° C.

It is found that the paints can be removed effectively from the coating.The paints used were yellow Prisma Color Acryl and blue Prisma ColorAcryl from SchullerEh′klar GmbH, Austria and also red Pinture PaintSpray, Montana Colors, S.L. Berlin.

COMPARATIVE EXAMPLE 1

A mixture according to EP 028 614 was prepared which contained 39 partsby weight of pentaerythrityl tetraacrylate, 59 parts by weight ofhexanediol diacrylate and 2 parts by weight of Darocur 1116 from Cibaand 1.6 parts by weight of 2-(N-ethylperfluorooctanesulphamido)ethylacrylate. The mixture was applied to a Makrolon sheet in accordance withInventive Example 1 using a spiral-wound wire doctor. After a levellingtime of two minutes the coating is cured using a high-pressure Hg lampat a speed of advance of 1 m/min and under a nitrogen atmosphere. As aresult of the forming operation, carried out in accordance withInventive Example 1, fine cracks appeared in the coating. The maximumelongation at break (cracking in the coat) is below 2%.

1. A coating composition for producing formable scratchproof coatings with dirt repellency effect, comprising A) from 1 to 30% by weight of a prepolymer obtainable by free-radically polymerizing a mixture comprising A1) from 1 to 10 parts by weight of at least one sulphur compound containing at least 3 thiol groups and A2) from 90 to 99 parts by weight of alkyl (meth)acrylates, B) from 0.2 to 10% by weight of fluoroalkyl (meth)acrylate according to the formula (II)

wherein the radical R₁ is a hydrogen atom or a methyl radical and n is an integer in the range from 2 to 10 C) from 20 to 80% by weight of polyfunctional (meth)acrylates, D) from 0.01 to 10% by weight of at least one initiator, E) from 2 to 75% by weight of at least one diluent and F) from 0 to 40% by weight of customary additives.
 2. The coating composition according to claim 1, wherein the prepolymer A) has a viscosity number to DIN ISO 1628-6 in the range from 8 to 15 ml/g measured in CHCl₃ at 20° C.
 3. The coating composition according to claim 1, wherein the alkyl (meth)acrylates used to prepare the prepolymer A) have 1 to 8 carbon atoms in the alcohol residue.
 4. The coating composition according to claim 3, wherein the prepolymer A) is prepared using a mixture of alkyl (meth)acrylates A2) containing at least 10% by weight of methyl (meth)methacrylate and/or ethyl (meth)acrylate and at least 2% by weight of alkyl (meth)acrylates having 3 to 8 carbon atoms.
 5. The coating composition according to claim 1, wherein the sulphur compound contains at least four thiol groups.
 6. The coating composition according to claim 5, wherein the sulphur compound is pentaerythritol tetrathioglycolate.
 7. The coating composition according to claim 1, wherein the coating composition contains from 0.5 to 2% by weight of fluoroalkyl (meth)acrylates in accordance with component B).
 8. The coating composition according to claim 1, wherein the initiator in accordance with component D) is a UV initiator.
 9. The coating composition according to claim 1, wherein the diluent in accordance with component E) comprises (meth)acrylates having 1 to 10 carbon atoms, styrenes and/or acrylonitrile.
 10. The coating composition according to claim 1, wherein component F) comprises UV absorbers and/or UV stabilizers.
 11. A scratchproof formable dirt-repellent moulding comprising a polymeric substrate and a scratch-proof coating obtained by a coating composition according to claim
 1. 12. The moulding according to claim 11, wherein the polymeric substrate comprises polymethyl methacrylate, polycarbonate, polyvinyl chloride, polystyrene, polyolefins, cycloolefin copolymers, polyesters and/or acrylonitrile/butadiene/styrene copolymers.
 13. The moulding according to claim 11, wherein the moulding has an impact strength to ISO 179/1 of at least 10 kJ/m².
 14. The moulding according to claim 11, wherein the polymeric substrate has a thickness in the range from 1 mm to 200 mm.
 15. The moulding according to claim 11, wherein the scratchproof coating has a coat thickness in the range from 1 to 50 μm.
 16. The moulding according to claim 11, wherein the haze of the moulding increases by not more than 5% after a scratch resistance test to DIN 52
 347. 17. The moulding according to claim 11, wherein the polymeric substrate has an elasticity modulus to ISO 527-2 of at least 1500 MPa.
 18. The moulding according to claim 11, wherein the moulding has a weathering stability to DIN 53 387 of at least 4000 hours.
 19. The moulding according to claim 11, wherein the moulding has a transparency to DIN 5033 of at least 70%.
 20. The moulding according to claim 11, wherein the contact angle of alpha-bromonaphthalene with the surface of the polymeric article at 20° C. is at least 50°.
 21. (canceled)
 22. A process for producing a scratchproof formable dirt-repellent moulding comprising applying the coating composition according to claim 1 to a polymeric substrate and curing the coating composition.
 23. A scratchproof formable dirt-repellant moulding prepared by the process as claimed in claim
 22. 